staging: rtl8187se: r8180_core.c: Inspect the return value of register_netdev()

Inspect the return value of register_netdev() in the driver probe routine and
return -ENODEV in case of error.

Signed-off-by: Kumar Amit Mehta <gmate.amit@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>